Rotary body position control apparatus

Abstract

A rotary shaft position control apparatus in which the rotary shaft is stopped in one revolution. After detection that a flux emitter on the shaft has passed a position detector, the shaft speed is set to a first speed. The first speed is continued until a product of the first speed and the elapsed time at the first speed after passing the position detector equals a predetermined constant. Then, the speed is reduced to a second speed. Finally, the shaft is stopped when the flux emitter again passes the detector.

What is claimed is: 
     
       1. A rotary body position control apparatus, comprising: a rotary body (6) driven to rotate by a driving source (2);   flux generation means (7) mounted on said rotary body;   a detector (8) fixedly provided for detecting magnetic flux generated by said flux generation means;   control means (10) for producing a speed change-over signal for changing-over, prior to final stopping of said rotary body, a rotational speed of said driving source from a first speed to a second speed smaller than said first speed on the basis of a detection output signal from said detector after said flux generation means reaches a predetermined point so as to stop said rotary body at a predetermined position with respect to said detector, said control means being provided with operation means (24) for producing said speed change-over signal at a timing when a product of said first speed and the time elapsed from arrival of said flux generation means (7) at said predetermined point becomes a predetermined value; and   a speed detection circuit (14) for detecting said rotational speed of said driving source (2) and for transferring a detection signal representing a result of detection to said control means (10) as a feedback signal; and   wherein said control means (10) includes:   a first circuit for receiving a first speed command;   a second circuit for receiving a second speed command;   a speed control circuit (15) for producing a speed control signal to said driving source (2); and   a speed-attainment detection circuit (19) for receiving the detection signal from said speed detection circuit (14), said speed-attainment detection circuit actuating said operation means (24) when said speed-attainment detection circuit detects that said rotary body (2) has reached said first speed, said operation means (24) producing the speed change-over signal so that connection of said speed control circuit (15) is changed from said first circuit to said second circuit.   
     
     
       2. A rotary body position control apparatus according to claim 1, further comprising a first and a second toothed wheel provided between said driving source (2) and said rotary body (6) for transmitting rotational driving force, and a gear-ratio reading circuit (20) provided in said control means (10) for reading a gear ratio of said first toothed wheel to said second toothed wheel. 
     
     
       3. A rotary body position control apparatus according to claim 1, wherein said control means causes said driving source to stop driving said rotary body at said second speed in response to a signal from said detector. 
     
     
       4. A rotary body position control apparatus according to claim 1, in which said speed-attainment detection circuit (19) compares an output signal of said detector (8) with the detection signal of said speed detection circuit (14) and actuates said operation means (24) when said output signal of said detector coincides with said detection signal. 
     
     
       5. A rotary body position control apparatus according to claim 1, in which said detector (8) periodically produces a first and a second output signal in accordance with the rotational speed of said rotary body (6). 
     
     
       6. A rotary body position control apparatus according to claim 1, in which said detector (8) periodically produces a first and a second output signal in accordance with the rotational speed of said rotary body (6), said first output signal being applied to said speed-attainment detection circuit (19), said second output signal being applied to said operation means (24) by said speed-attainment detection circuit (19). 
     
     
       7. A rotary body position control apparatus according to claim 1, in which said detector (8) periodically produces a first and a second output signal in accordance with the rotational speed of said rotary body (6), said first output signal being a voltage signal which becomes zero when a center of said detector (8) coincides with a center of said flux generation means (7) and which assumes maximum levels opposite in polarity to each other when said center of said detector (8) corresponds respectively to opposite ends of said flux generation means. 
     
     
       8. A rotary body position control apparatus according to claim 1, in which said detector (8) periodically produces a first and a second output signal in accordance with the rotational speed of said rotary body (6), said second output signal being a voltage signal which is generated with a predetermined polarity and at a predetermined level only in a period in which a center of said detector (8) is opposite to said flux generation means (7).